The bad news is that we only know of one
single broker who can organise short term car insurance for drivers
under the age of 21; in this case the minimum age limit is 18
although they can also cover drivers up to 75, subject to the usual
conditions of course. The
good news is that they have a panel of insurers to choose from, and
these insurers all have different criteria they use in deciding who
they can, or cannot, offer cover to, and what they will charge for
this, so you have a much better chance
of finding a suitable policy.

Younger drivers do pose a statistically higher risk of accidents so
you they almost certainly find that a higher excess will be
required, probably in the region of £500 upwards. There may well be
other limitations too, and you are strongly advised to read through
the policy documents before deciding on whether or not to buy cover;
these documents are easy to access and are written in plain English
so it is fairly easy to find out exactly what is covered, and
perhaps more importantly what is not.

Since you may be offered more than one policy it is not really
possible to detail the exact terms and conditions that you will be
offered, but in general you will be expected to drive a fully
roadworthy vehicle in a sensible manner, and look after it properly;
leaving it parked with a boot, window or sunroof open will almost
certainly lead to refusal of a claim for theft or damage to the
vehicle, and leaving the keys where they can be easily stolen can
also cause a problem. In common with practically every other
insurance policy on the market dangerous areas such as unmade roads,
military establishments and hazardous chemical manufacturers should
be avoided.